What is modified format in letter writing?

There isn't a universally recognized term called "modified format" in letter writing. It's possible you're referring to a specific style of letter format that might be unique to a particular organization or field.

However, there are several common letter formats, including:

* Block Format: This is the most common and simplest format. All elements (date, inside address, salutation, body, closing, and signature) are aligned to the left margin.

* Semi-Block Format: Similar to block format, but the date, closing, and signature are aligned to the center of the page.

* Modified Block Format: This format is like block format, but the first line of each paragraph is indented.

It's likely that "modified format" refers to a variation of one of these standard formats with slight modifications to suit specific needs.

To understand the "modified format" you're interested in, you'll need to provide more context:

* Where did you encounter this term? (Was it in a specific document, a class, or a job application?)

* What kind of letter is it? (Business letter, personal letter, etc.)

Once I have more information, I can help you understand the specific format being referred to.